This walkthrough for The Goonies will provide you with the following information:

Fully detailed maps, including the location of every hidden object that each stage contains

A brief walkthrough that details which directions to move in in order to clear each stage quickly

The method of input required to reveal hidden objects, contained in a drop down window to prevent spoilers

The equipment items and hidden characters that you can reveal in the stage and a bit about their purpose

Naturally, if you look at the maps, you are going to see where objects are hidden. If you don't want to know this information, try to play through the stage a little bit on your own. Of course, knowing where the objects exist is only half of the battle. The other half is knowing which specific input to make in order to reveal the objects so that you can collect them. The input method is contained in a spoiler window, and will not be shown to you unless you click the [show] link on the left. If you do, you will see the input method for both the odd levels and the even levels, which differ slightly. In order to reveal an object, you must enter the correct input at the location where an item is indicated to appear. If the input method happens to be +, be careful if you happen to have bombs in your inventory as you will ignite one of them.

All hidden characters that you reveal can be collected for 5000 points. However, if you are not quick enough and fail to collect them after you make them appear, they disappear, and you will be awarded only 1000 points instead. Some hidden characters move, so you will need to catch them if you want the 5000 points.

There are 6 stages and 3 passages, which you move through in a sequential order with one exception. You may opt to take a warp from Stage 3 directly to Stage 5. Additionally, if you do not have all five rescued Goonies by the time you enter the skull mouth in Passage C, you will be sent back to the first stage and forced to repeat the same level of difficulty. So try not to exit any stage without finding that stage's captured Goonie first.

Generally, if you are playing at higher levels, enemies will respawn and move faster, and deal more damage to you. For example, both Fratelli brothers will appear in Stage 1 of Level 2+, and there is a higher chance of yellow rats appearing in all stages.